Semiconductor device and method for forming the same

ABSTRACT

A method for forming a semiconductor device includes the steps of providing a substrate having a memory region and a logic region, forming a memory stack structure on the memory region, forming a passivation layer covering a top surface and sidewalls of the memory stack structure, forming a first interlayer dielectric layer on the passivation layer, performing a post-polishing etching back process to remove a portion of the first interlayer dielectric layer and a portion of the passivation layer on the top surface of the memory stack structure, forming a second interlayer dielectric layer on the first interlayer dielectric layer and directly contacting the passivation layer, and forming an upper contact structure through the second interlayer dielectric layer and the passivation layer on the top surface of the memory stack structure to contact the memory stack structure.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to a semiconductor device andmethod for forming the same. More particularly, the present inventionrelates to a magnetoresistive random access memory (MRAM) and method forforming the same.

2. Description of the Prior Art

A magnetoresistive random access memory (MRAM) is a kind of non-volatilememory that has drawn a lot of attention in this technology fieldrecently regarding that it may incorporate advantages of other kinds ofmemories. For example, an MRAM device may have an operation speedcomparable to SRAMs, the non-volatile feature and low power consumptioncomparable to flash, the high integrity and durability comparable toDRAM. More important, the process for forming an MRAM device may beconveniently incorporated into existing semiconductor manufacturingprocesses.

A typical MRAM cell structure usually comprises a memory stack structurecomprising magnetic tunnel junction (MTJ) disposed between the lower andupper interconnecting structures. Unlike conventional memories thatstore data by electric charge or current flow, an MRAM cell stores databy applying external magnetic fields to control the magnetic polarityand tunneling magnetoresistance (TMR) of the MTJ.

The manufacturing of MRAM devices is still confronted with challenges.For example, the memory stack structure is usually covered by apassivation layer for protection and passivation, and then covered by aninterlayer dielectric layer. However, the passivation layer may cause anetching burden during the etching process for forming an upper contactstructure for electrically contacting the memory stack structure, andresults in problems such as bottom shrinkage or non-opening (due toetching stop) of the upper contact structure. The interconnectingquality between the memory stack structure and the upper contactstructure may be influenced, which may cause errors when reading orwriting data in the MRAM.

SUMMARY OF THE INVENTION

In light of the above, the present invention is directed to provide asemiconductor device such as a magnetoresistive random access memory(MRAM) and method for forming the same. By performing a post-polishingetching back process to remove the interlayer dielectric layer and aportion of the passivation layer on the top surface of the memory stackstructure after planarizing the interlayer dielectric layer. In thisway, the problems such as bottom shrinkage or non-opening of the uppercontact structure may be reduced.

In one embodiment of the present invention, a method for forming asemiconductor device is disclosed and includes the following steps.First, a substrate having a memory region and a logic region isprovided. Subsequently, a memory stack structure is formed on the memoryregion of the substrate. A passivation layer is then formed on thesubstrate and covers a top surface and sidewalls of the memory stackstructure. After that, a first interlayer dielectric layer is formed onthe passivation layer. A post-polishing etching back process is thenperformed to remove a portion of the first interlayer dielectric layerand a portion of the passivation layer on the top surface of the memorystack structure. Afterward, a second interlayer dielectric layer isformed on the first interlayer dielectric layer and directly contactsthe passivation layer. Following, an upper contact structure is formedand penetrates through the second interlayer dielectric layer and thepassivation layer on the top surface of the memory stack structure tocontact the memory stack structure.

In another embodiment of the present invention, a semiconductor deviceis disclosed. The semiconductor device includes a substrate having alogic region and a memory region. A first interlayer dielectric layer isdisposed on the substrate. A second interlayer dielectric layer isdisposed on the first interlayer dielectric layer. A memory stackstructure is disposed in the first interlayer dielectric layer on thememory region of the substrate. A passivation layer covers a top surfaceand sidewalls of the memory stack structure. The second interlayerdielectric layer directly contacts the passivation layer. An uppercontact structure penetrates through the second interlayer dielectriclayer and the passivation layer on the top surface of the memory stackstructure to contact the memory stack structure.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 to FIG. 10 are schematic cross-sectional diagrams illustratingthe steps of a method of forming a semiconductor device according to anembodiment of the present invention.

DETAILED DESCRIPTION

To provide a better understanding of the present invention to those ofordinary skill in the art, several exemplary embodiments of the presentinvention will be detailed as follows, with reference to theaccompanying drawings using numbered elements to elaborate the contentsand effects to be achieved. The drawings illustrate some of theembodiments and, together with the description, serve to explain theirprinciples. Relative dimensions and proportions of parts of the drawingshave been shown exaggerated or reduced in size, for the sake of clarityand convenience in the drawings. The same reference signs are generallyused to refer to corresponding or similar features in modified anddifferent embodiments. These embodiments are described in sufficientdetail to enable those skilled in the art to practice the invention.Other embodiments may be utilized and that structural, logical andelectrical changes may be made without departing from the spirit andscope of the present invention.

The semiconductor structure illustrated in the embodiment in thefollowing description may be a magnetic random access memory (MRAM). Itshould be understood that the present invention may be applied to othersemiconductor devices including components integrally manufactured withback-end-on-line (BEOL) process, such as ferroelectric random accessmemory (FRAM), phase-change random access memory (PRAM), or resistiverandom access memory (RRAM), but is not limited thereto.

Please refer to FIG. 1 to FIG. 10 , which are schematic cross-sectionaldiagrams illustrating the steps of a method of forming a semiconductordevice according to an embodiment of the present invention. As shown inFIG. 1 , first, a substrate 10 is provided. The substrate 10 includes alogic region 14 and a memory region 16. Subsequently, an etching stoplayer 202 and a dielectric material layer 204 are successively formed onthe substrate 10. Afterward, a memory stack layer 300 is formed on thedielectric material layer 204.

The substrate 10 may include a multi-layered structure. For example, thesubstrate 10 may include a semiconductor substrate 101 and an interlayerdielectric layer 102 on the semiconductor substrate 101. Thesemiconductor substrate 101 may be a silicon substrate, asilicon-on-insulator (SOI) substrate, or a Group III-V semiconductorsubstrate, but is not limited thereto. The semiconductor substrate 101may include active components such as metal-oxide semiconductor (MOS)transistors, passive components, conductive layers, and dielectriclayers such as isolation structures and interlayer dielectric (ILD)layers formed therein. For the sake of simplicity, those components andstructural layers are not shown in the diagram.

The interlayer dielectric layer 102 may include dielectric materialssuch as silicon oxide (SiO₂) or low-k dielectric materials such asfluorinated silica glass (FSG), silicon oxycarbide (SiCOH),spin-on-glass, porous low-k dielectric material, organic dielectricpolymers, or a combination thereof, but is not limited thereto.

The interlayer dielectric layer 102 may include interconnectingstructures formed therein. For example, a lower interconnectingstructure 104 formed in the logic region 14 of the interlayer dielectriclayer 102, and a lower interconnecting structure 106 formed in thememory region 16 of the interlayer dielectric layer 102. The lowerinterconnecting structure 104 and the lower interconnecting structure106 may include metal materials, such as tungsten (W), copper (Cu),aluminum (Al), or other suitable metal materials, but are not limitedthereto. According to an embodiment, the lower interconnecting structure104 and the lower interconnecting structure 106 respectively includecopper (Cu).

The etching stop layer 202 is disclosed between the interlayerdielectric layer 102 and the dielectric material layer 204. The etchingstop layer 202 may include dielectric materials such as silicon nitride(SiN), silicon carbon nitride (SiCN), silicon oxynitride (SiON), ornitride doped silicon carbide (NDC), but is not limited thereto. Thedielectric material layer 204 may include silicon oxide (SiO₂) or low-kdielectric materials.

A plurality of contact plugs 108 may be formed in the memory region 16and through the dielectric material layer 204 and the etching stop layer202 to directly contact and electrically coupled to the lowerinterconnecting structure 106 in the memory region 16. The contact plugs108 may include metal materials, such as tungsten (W), copper (Cu),aluminum (Al), or other suitable metal materials, but are not limitedthereto. According to an embodiment, the contact plugs 108 includetungsten (W).

The memory stack layer 300 may include, from bottom to top, a bottomelectrode layer 302, a magnetic tunneling junction (MTJ) stack layer304, a capping layer 314 and a top electrode layer 316. The bottomelectrode layer 302 and the top electrode layer 316 respectively includeconductive materials, such as titanium (Ti), tantalum (Ta), titaniumnitride (TiN), tantalum nitride (TaN), or a combination thereof, but arenot limited thereto. The bottom electrode layer 302 and the topelectrode layer 316 may include the same or different conductivematerials. The MTJ stack layer 304 may comprise multiple layersincluding, from bottom to top, a pinning layer 306, a pinned layer 308,a tunneling layer 310 and a free layer 312. The pinning layer 306 maycomprise anti-ferromagnetic (AFM) material such as PtMn, IrMn, PtIr orthe like, but is not limited thereto. The pinning layer 306 is used topin or fix nearby ferromagnetic layers to a particular magneticpolarity. The pinned layer 308 and the free layer 312 may comprise thesame or different ferromagnetic materials such as Fe, Co, Ni, FeNi,FeCo, CoNi, FeB, FePt, FePd, CoFeB, or the like, but are not limitedthereto. The magnetic polarity of the pinned layer 308 is pinned(anti-ferromagnetic coupled) by the pinning layer 306, while themagnetic polarity of the free layer 312 may be changed by an externalmagnetic field. The tunneling layer 310 is sandwiched between the pinnedlayer 308 and the free layer 312 and may comprise insulating materialssuch as MgO, Al₂O₃, NiO, GdO, Ta₂O₅, MoO₂, TiO₂, tungsten oxide (WO₂),or a combination thereof, but is not limited thereto. The pinning layer306, the pinned layer 308, the tunneling layer 310 and the free layer312 may respectively comprise single or multiple layers having athickness ranges from several angstroms (Å) to dozens of nanometers(nm). The capping layer 314 may comprise metals or metal oxides, such asaluminum (Al), magnesium (Mg), tantalum (Ta), ruthenium (Ru), tungstendioxide (WO₂), nickel oxide (NiO), magnesium oxide (MgO), aluminum oxide(Al₂O₃), tantalum oxide (Ta₂O₅), molybdenum dioxide (MoO₂), titaniumoxide (TiO₂), gadolinium oxide (GdO), or manganese oxide (MnO), or acombination thereof, but is not limited thereto.

Please refer to FIG. 2 . Subsequently, a patterning process is performedto pattern the memory stack layer 300 to form a plurality of memorystack structures 330 on the memory region 16 substrate 10 and alsoremove the memory stack layer 300 on the logic region 14 of thesubstrate 10.

According to an embodiment of the present invention, the patterningprocess for forming the memory stack structures 330 may include thefollowing steps. First, a patterned hard mask layer (not shown), such asa patterned silicon oxide layer or a patterned silicon nitride layer,may be formed on the top electrode layer 316. After that, a first stageof etching, such as a reactive ion etching (RIE) process, using thepatterned hard mask layer as an etching mask may be performed to etchthe top electrode layer 316, thereby transferring the pattern of thepatterned hard mask layer to the top electrode layer 316. Afterward, asecond stage of etching, such as an ion beam etching (IBE) process,using the patterned top electrode layer 316 as an etching mask may beperformed to etch the capping layer 314, the MTJ stack layer 304 and thebottom electrode layer 302, thereby transferring the pattern of thepatterned top electrode layer 316 to the capping layer 314, the MTJstack layer 304 and the bottom electrode layer 302. As a result, thememory stack structures 330 as shown in FIG. 2 are obtained. Accordingto an embodiment of the present invention, the dielectric material layer204 exposed from the memory stack structures 330 on the memory deviceregion 16 and the dielectric material layer 204 on the logic deviceregion 14 may be over-etched by the second stage of etching (the IBEprocess) to ensure the unnecessary memory stack layer 300 being removed.Accordingly, the dielectric material layer 204 may have a recessed topsurface 204 a after the patterning process.

Please continue to refer to FIG. 2 . Subsequently, a passivation layer402 may be formed on the substrate 10 and conformally cover a topsurface and sidewalls of each memory stack structure 330 and therecessed top surface 204 a of the dielectric material layer 204.According to an embodiment of the present invention, optionally, aremoving process such as a photo-lithography etching process may beperformed to remove the passivation layer 402 on the logic region 14 ofthe substrate 10, and the surface of the dielectric material layer 204on the logic region 14 may be exposed.

The passivation layer 402 may be formed by chemical vapor deposition(CVD) and may include an insulating material such as silicon nitride(SiN), silicon carbon nitride (SiCN), silicon oxynitride (SiON), or acombination thereof, but is not limited thereto. According to anembodiment of the present invention, the passivation layer 402 includessilicon nitride (SiN). According to an embodiment, the passivation layer402 is formed in-situ after the second stage of etching, i.e. the IBEprocess, to prevent the magnetic tunneling junction (MTJ) stack layer304 exposed from the sidewalls 330 b of the memory stack structures 330from being oxidized or absorbing contaminations.

As shown in FIG. 2 . A portion of the passivation layer 402 covering therecessed top surface 204 a of the dielectric material layer 204 may havea thickness T1. A portion of the passivation layer 402 covering the topsurface 330 a of the memory stack structure 330 may have a thickness T2.A portion of the passivation layer 402 covering the sidewalls 330 b ofthe memory stack structure 330 may have a thickness T3. According to anembodiment of the present invention, the thickness T1 and the thicknessT2 may approximately be equal to each other, and the thickness T3 issmaller than the thickness T1 and the thickness T2. For example, thethickness T3 may be between 60% and 80% of the thickness T1 or of thethickness T2. According to an embodiment of the present invention, thethickness T1 and the thickness T2 may be between 300 Å and 360 Å, andthe thickness T3 may be between 180 Å and 220 Å.

Please refer to FIG. 3 . Subsequently, a dielectric material layer 206is formed on the substrate 10 in a blanket manner. The dielectricmaterial layer 206 completely covers the logic region 14 and the memoryregion 16 of the substrate 10 and fills the space between the memorystack structures 330. The memory stack structures 330 make the surfaceof the dielectric material layer 206 on the memory device region 16 ofthe substrate 10 be higher than the surface of the dielectric materiallayer 206 on logic device region 14 of the substrate 10. The dielectricmaterial layer 206 may include dielectric materials such as siliconoxide (SiO₂) or low-k dielectric materials such as fluorinated silicaglass (FSG), silicon oxycarbide (SiCOH), spin on glass, porous low-kdielectric material, organic dielectric polymers, or a combinationthereof, but is not limited thereto.

Please refer to FIG. 4 . Subsequently, a mask layer 208 (such as aphotoresist layer) is formed on the dielectric material layer 206. Themask layer 208 is then patterned to form an opening exposing a portionof the dielectric material layer 206 on the memory region 16 of thesubstrate 10. Following, a pre-polishing etching back process EB1 (suchas a dry etching process) using the mask layer 208 as an etching mask isperformed to etch away a portion of the dielectric material layer 206from the opening of the mask layer 208 until a surface of the dielectricmaterial layer 206 on the memory region 16 is higher than a surface ofthe dielectric material layer 206 on the logic region 14 by a height H1.According to an embodiment of the present invention, a range of theheight H1 may be between 200 Å and 300 Å, but is not limited thereto.

Please refer to FIG. 5 . Subsequently, after removing the mask layer208, a polishing process CMP1 is performed to planarize the dielectricmaterial layer 206. According to an embodiment of the present invention,due to the loading effect of the polishing process CMP1, a surface ofthe dielectric material layer 206 on the memory region 16 may still behigher than a surface of the dielectric material layer 206 on the logicregion 14 by a height H2 after the polishing process CMP1. The height H2may be approximately equal to or slightly smaller than the height H1.For example, the height H2 may be between 200 Å and 300 Å, or between160 Å and 200 Å, but is not limited thereto. After the polishing processCMP1, the etching stop layer 202, the dielectric material layer 204 andthe dielectric material layer 206 collectively form a first interlayerdielectric layer 200 of the semiconductor device of the presentinvention. It should be noted that at this process stage, thepassivation layer 402 on the memory stack structure 330 is still coveredby the dielectric material layer 206 and is not exposed.

Please refer to FIG. 6 . Subsequently, a mask layer 210 (such as aphotoresist layer) is formed on the dielectric material layer 206. Themask layer 210 is then patterned to form an opening exposing a portionof the dielectric material layer 206 on the memory region 16 of thesubstrate 10. Following, a post-polishing etching back process EB2 (suchas a dry etching process) using the mask layer 210 as an etching mask isperformed to etch away a portion of the dielectric material layer 206from the opening of the mask layer 210 to expose the passivation layer402 on the top surface 330 a of the memory stack structure 330. Thepost-polishing etching back process EB2 continues to etch away a portionof the passivation layer 402 without exposing any portion of the memorystack structure 330. As shown in FIG. 6 , after the post-polishingetching back process EB2, the passivation layer 402 on the top surface330 a of the memory stack structure 330 may have a thickness T4.According to an embodiment of the present invention, preferably, thethickness T4 may be between 30% and 50% of the thickness of the etchingstop layer 602 of the second interlayer dielectric layer 600 formed in alater process step (shown in FIG. 10 ). For example, the thickness T4may be between 60 Å and 100 Å, but is not limited thereto.

Please continue to refer to FIG. 6 . After the post-polishing etchingback process EB2, a surface of the dielectric material layer 206 on thememory region 16 of the substrate 10 may be lower than a surface of thedielectric material layer 206 on the logic region 14 of the substrate10, thereby forming a step portion 212 of the dielectric material layer206 having a step-height H3 near the boundary between the logic region14 and the memory region 16. According to an embodiment of the presentinvention, the step-height H3 may be between 100 Å and 150 Å, but is notlimited thereto.

Please refer to FIG. 7 and FIG. 8 . Subsequently, after removing themask layer 210, a dual damascene process may be performed to form afirst interconnecting structure 510 in the first interlayer dielectriclayer 200. In detail, a trench 503 may be formed in the logic region 14and through the dielectric material layer 206, the dielectric materiallayer 204 and the etching stop layer 202 of the first interlayerdielectric layer 200 to expose a surface of the lower interconnectingstructure 104. After that, a conductive layer 500 is formed on the firstinterlayer dielectric layer 200 and filling up the trench 503. Theconductive layer 500 may include metals, such as tungsten (W), copper(Cu), aluminum (Al), or other suitable metal materials, but is notlimited thereto. According to an embodiment of the present invention,the conductive layer 500 may include copper (Cu). As shown in FIG. 8 ,the conductive layer 500 may directly contact the passivation layer 402on the top surface 330 a of the memory stack structure 330. According toan embodiment of the present invention, the conductive layer 500 mayinclude a barrier layer (not shown) interfacing the dielectric materiallayer 206, the dielectric material layer 204, the etching stop layer 202and the lower interconnecting structure 104.

As shown in FIG. 9 , a metal polishing process CMP2 is then performed toremove the conductive layer 500 outside the trench 503 until a surfaceof the dielectric material layer 206 is exposed. The conductive layer500 remaining filling in the trench 503 becomes the firstinterconnecting structure 510. The first interconnecting structure 510directly contacts and is electrically coupled to the lowerinterconnecting structure 104 in the logic region 14 of the substrate10.

It should be noted that, by using a polishing slurry that has highremoval rate for the conductive layer 500 and small removal rate for thedielectric material layer 206 and the passivation layer 402 (highselectivity between the conductive layer 500 and the dielectric materiallayer 206 and the passivation layer 402) during the metal polishingprocess CMP2, the metal polishing process CMP2 may be well controlled tostop on the dielectric material layer 206 and the passivation layer 402.In this way, the metal polishing process CMP2 will not significantlyreduce the thicknesses of the dielectric material layer 206 and thepassivation layer 402, and will not significantly influence thethrough-substrate (or through wafer) uniformity of the dielectricmaterial layer 206 and the passivation layer 402. According to anembodiment of the present invention, after the metal polishing processCMP2, a step portion 212 of the dielectric material layer 206 having astep-height H4 may appear near the boundary between the logic region 14and the memory region 16. The step-height H4 may be approximately equalto or smaller than the step-height H3. For example, the step-height H4may be between 100 Å and 150 Å, but is not limited thereto. After themetal polishing process CMP2, the passivation layer 402 on the topsurface 330 a of the memory stack structures 330 may have a thicknessT5. The thickness T5 may be approximately equal to or smaller than thethickness T4. For example, the thickness T5 may be between 60 Å and 100Å, but is not limited thereto.

Please refer to FIG. 10 . Subsequently, a second interlayer dielectriclayer 600 is formed on the first interlayer dielectric layer 200. Thesecond interlayer dielectric layer 600 may include an etching stop layer602 and a dielectric material layer 606 disposed on the etching stoplayer 602. Following, a second interconnecting structure 610 and anupper contact structure 612 are formed in the second interlayerdielectric layer 600 on the logic region 14 and the memory region 16,respectively.

As shown in FIG. 10 . The etching stop layer 602 directly contacts thepassivation layer 402, the dielectric material layer 206 and theconductive layer 500, and conformally covers the step portion 212 of thedielectric material layer 206 near the boundary between the logic region14 and the memory region 16. The etching stop layer 602 may includedielectric materials such as silicon nitride (SiN), silicon carbonnitride (SiCN), silicon oxynitride (SiON), or nitride doped siliconcarbide (NDC), but is not limited thereto. According to an embodiment ofthe present invention, the etching stop layer 602 and the etching stoplayer 202 include a same material, such as nitride doped silicon carbide(NDC). According to an embodiment of the present invention, a thicknessof the etching stop layer 602 may be between 180 Å and 220 Å.

The dielectric material layer 606 may include dielectric materials suchas silicon oxide (SiO₂) or low-k dielectric materials such asfluorinated silica glass (FSG), silicon oxycarbide (SiCOH),spin-on-glass, porous low-k dielectric material, organic dielectricpolymers, or a combination thereof, but is not limited thereto.According to an embodiment of the present invention, the dielectricmaterial layer 606 and the dielectric material layer 206 may include asame material, such as at least one of the low-k dielectric materialsillustrated above.

The upper contact structure 612 penetrates through the second interlayerdielectric layer 600 on the memory region 16 and the passivation layer402 on the top surface 330 a of the memory stack structure 330 tocontact the top electrode layer 316 of the memory stack structure 330.The second interconnecting structure 610 penetrates through the secondinterlayer dielectric layer 600 on the logic region 14 to contact thefirst interconnecting structure 510. According to an embodiment of thepresent invention, the upper contact structure 612 and the secondinterconnecting structure 610 may be formed concurrently in the secondinterlayer dielectric layer 600 by, for example, a dual damasceneprocess. The upper contact structure 612 and the second interconnectingstructure 610 may respectively include a conductive layer 608. Theconductive layer 608 may include metals, such as tungsten (W), copper(Cu), aluminum (Al), or other suitable metal materials, but is notlimited thereto. According to an embodiment of the present invention,the conductive layer 608 may include copper (Cu). According to anembodiment of the present invention, the conductive layer 608 of theupper contact structure 612 may include a barrier layer (not shown)interfacing the dielectric material layer 606, the etching stop layer602, the passivation layer 402, and the top electrode layer 316 of thememory stack structure 330. The conductive layer 608 of the secondinterconnecting structure 610 may include a barrier layer (not shown)interfacing the dielectric material layer 606, the etching stop layer602, and the conductive layer 500 of the first interconnecting structure510.

Please continue to refer to FIG. 10 . According to one embodiment of thepresent invention, a semiconductor device 100 is provided. Thesemiconductor device 100 includes a substrate 10 having a logic region14 and a memory region 16, and a first interlayer dielectric layer 200on the substrate 10. A portion of the first interlayer dielectric layer200 on the memory region 16 has a thickness T6, and another portion ofthe first interlayer dielectric layer 200 on the logic region 14 has athickness T7. The thickness T6 is smaller than the thickness T7, therebyforming a step portion 212 of the dielectric material layer 206 near theboundary between the logic region 14 and the memory region 16. Accordingto an embodiment of the present invention, the thickness T6 and thethickness T7 may be different by approximately between 100 Å and 150 Å.The step-height H4 of the step portion 212 may be between 100 Å and 150Å. The second interlayer dielectric layer 600 is disposed on the firstinterlayer dielectric layer 200 and covers the step portion 212 of thedielectric material layer 206. At least a memory stack structure 330 isdisposed in the first interlayer dielectric layer 200 on the memoryregion 16 of the substrate 10. A first interconnecting structure 510 isdisposed in the first interlayer dielectric layer 200 on the logicregion 14. A height of the memory stack structure 330 is smaller than aheight of the first interconnecting structure 510. The passivation layer402 is provided to cover the top surface 330 a and sidewalls 330 b ofthe memory stack structures 330, wherein the second interlayerdielectric layer 600 directly contacts the passivation layer 402, and aportion of the passivation layer 402 is sandwiched between the topsurface 330 a of the memory stack structures 330 and the secondinterlayer dielectric layer 600. The portion of the passivation layer402 sandwiched between the top surface 330 a of the memory stackstructures 330 and the second interlayer dielectric layer 600 has thethickness T5, and the thickness T5 is smaller than the thickness T3 ofanother portion of the passivation layer 402 on the sidewalls 330 b ofthe memory stack structures 330. According to an embodiment of thepresent invention, the thickness T5 may be between 60 Å and 100 Å, andthe thickness T3 may be between 180 Å and 220 Å. The upper contactstructure 612 penetrates through the second interlayer dielectric layer600 and the passivation layer 402 on the top surface 330 a of the memorystack structure 330 to contact the memory stack structure 330.

In conclusion, one feature of the present invention is that, byperforming a post-polishing etching back process to remove theinterlayer dielectric layer and a portion of the passivation layer onthe top surface of the memory stack structure, the thickness of thematerial that the bottom portion of the upper contact structure needs topenetrate through and the thickness of the material that the bottomportion of the second interconnecting structure needs to penetratethrough may be closer, which is beneficial for integrally forming theupper contact structure and the second interconnecting structure.Furthermore, it is also possible to control the post-polishing etchingback process to yield the passivation layer with better thicknessuniformity on the top surface of the memory stack structure. In thisway, the difficulty caused by the thickness variation of the firstinterlayer dielectric layer after the polishing process to the etchingprocess of forming the upper contact structure and the secondinterconnecting structure may be reduced. Overall, when the uppercontact structure and the second interconnecting structure areintegrally formed at the same time, the problems such as bottomshrinkage or non-opening of the upper contact structure may be reduced,and a better product yield may be achieved.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A semiconductor device, comprising: a substratehaving a logic region and a memory region; a first interlayer dielectriclayer disposed on the substrate, wherein a thickness of the firstinterlayer dielectric layer on the memory region is smaller than athickness of the first interlayer dielectric layer on the logic region;a second interlayer dielectric layer disposed on the first interlayerdielectric layer; a memory stack structure disposed in the firstinterlayer dielectric layer on the memory region; a passivation layercovering a top surface and sidewalls of the memory stack structure,wherein the second interlayer dielectric layer directly contacts thepassivation layer; and an upper contact structure through the secondinterlayer dielectric layer and the passivation layer on the top surfaceof the memory stack structure and directly contacting the memory stackstructure.
 2. The semiconductor device according to claim 1, wherein thethickness of the first interlayer dielectric layer on the logic regionis different from the thickness of the first interlayer dielectric layeron the memory region by between 100 Å and 150 Å.
 3. The semiconductordevice according to claim 1, wherein the first interlayer dielectriclayer comprises a step portion near a boundary between the logic regionand the memory region.
 4. The semiconductor device according to claim 3,wherein a step-height of the step portion is between 100 Å and 150 Å. 5.The semiconductor device according to claim 1, wherein a portion of thepassivation layer sandwiched between the top surface of the memory stackstructure and the second interlayer dielectric layer has a thicknessbetween 60 Å and 100 Å.
 6. The semiconductor device according to claim1, further comprising: a first interconnecting structure disposed in thefirst interlayer dielectric layer on the logic region; and a secondinterconnecting structure disposed in the second interlayer dielectriclayer and contacting the first interconnecting structure, wherein aheight of the memory stack structure is smaller than a height of thefirst interconnecting structure.
 7. The semiconductor device accordingto claim 1, wherein the second interlayer dielectric layer comprises: anetching stop layer contacting the first interlayer dielectric layer andthe passivation layer; and a dielectric material layer on the etchingstop layer.
 8. The semiconductor device according to claim 7, whereinthe etching stop layer comprises nitride doped silicon carbide, thedielectric material layer comprises a low-k dielectric material, and thepassivation layer comprises silicon nitride.